Moving again to a distributed setting, some progress has been made with the introduction of the Flexible Score Aggregation (FSA) [1]}, algorithm. FSA is an instance optimal algorithm and it is the result of a combination between the FA and TA algorithms introduced in [sec:sec2.1]Section 2.1. FSA allows the user to calculate the set \(ND_{k}\)  which, when \(k\)  is equal to one, matches the result of ND. This algorithm is very efficient and effective, leading to a reduction in the result set within cardinality, even for large datasets. However, this is not enough, since FSA still presents a quadratic complexity, while top-k queries are far better in terms of raw performance.
